Pitless units are used throughout the world in potable water supply wells, booster pumping stations and geothermal (well to well) pumping applications. They form connectors each implemented at a well casing of the pumping system by which a pump at a bottom of the well may be accessed. Thus, water typically flows up from the pump, through the connector defined by the pitless unit, and downstream to a remainder of the pumping system.
Pitless units comprise a discharge housing and an internal spool. The surfaces of both components that are in contact with the water stream flowing through the connector, sometimes termed as the wetted surfaces of the pitless unit, are susceptible to corrosion over time. Maintaining the water purity also is considered important in water well applications including prevention of contamination and/or potential bacteria growth.
For example, in water supply wells, raw water typically contains a plurality of hard water ions which may effect corrosion on the pitless unit which is typically made of mild steel, alternatively termed carbon steel, which is susceptible to corrosion.
In booster station applications, where the water has already been treated commonly by reverse osmosis before passing through the pitless unit in the booster station, this form of treatment may cause the water to become corrosive.
There exist commercially available pitless units which are one of galvanized and epoxy coated so as to protect against corrosion. More specifically, in galvanization, a thin zinc based galvanized coating (approximately 0.00″-0.005″ thick) onto the base metal typically which is carbon steel. In epoxy coating, a coating of NSF 61 approved epoxy (approximately 0.006″ to 0.020″ thick) is applied onto the surface of the base metal which forms each of the housing and spool.
However, there are some potential shortcoming associated with the above mentioned non-corrosive coatings. For example, these coatings are susceptible to chipping, often during installation of the connector, and de-bonding or delamination either of which may expose the base metal to contact with the water flowing through the connector.
Though areas of a coating which are chipped may be repaired by application of a painted coating in the field, the resulting coating including the original coating and the painted spots does not provide perform the same in terms of corrosion protection as a continuous and uninterrupted coating as originally applied. As such, premature corrosion and failure is more likely to result.
Further, it will be appreciated that in the case of galvanized pitless units, galvanized coatings inherently are sacrificial in nature and thus have limited service life.
Additionally, it will be appreciated that a quality of an epoxy coating is dependent on preparation of the base material prior to receiving the coating thereon. If a surface of the base material was not prepped properly the epoxy coating does not adhere thereto and the coating will delaminate or peel away over a period of time. Thus, with epoxy coatings there exists the possibility that the coating will break or spall during the service life of the connector.
The Applicant has developed a novel solution for a pitless unit which may have better non-corrosion performance than currently commercially available pitless units using galvanized or epoxy coatings for non-corrosion purposes.